The invention relates to a hybrid hydraulic drive system for all types of terrestrial vehicles, including vehicles running on rails, using as prime mover, any rotational device able to give an output torque. A variable hydraulic pump may be connected to the prime mover and acts as a “power integrator”, receiving hydraulic power from the accumulator, mechanical power from the prime mover, or a combination thereof, to supply the desired flow and necessary pressure to the hydraulic motors during operation. A second variable pump reloads the accumulator with the remnant power available, if any, during the whole cycle. The accumulator may be quite large and may also be used partially or totally, as the main load bearing full frame for all terrestrial vehicles. The braking energy may be returned to the accumulator. The whole vehicle is controlled by electronics, and in one embodiment uses only one joystick or pedal to control speed, direction, acceleration, braking and in some cases including steering.
The present invention thus relates to a series hybrid hydraulic drive system than can be applied with advantage to all terrestrial vehicles, with or without rails, including but not limited to industrial, commercial and military applications as well as to passenger vehicles. The prime mover, typically, but not necessarily, a conventional motor such as an internal combustion engine, or an electrical motor, are used to their maximum efficiency when running.
An accumulator, which is a device that operates as an energy storage device or storage reservoir for energy, is provided on the vehicle and is positioned as the load bearing frame of a vehicle, reloading when the vehicle is braking and/or when the prime mover is running and there is additional energy from the prime mover, and/or the accumulator is providing energy.
Hybrid hydraulic regenerative drive systems are known and have been applied to motor vehicles in the past. Parallel hydraulic systems are also available and have been successful in harnessing the braking energy of the vehicle and storing it in an accumulator, to be used to accelerate the vehicle and thereby provide acceptable energy savings.
The parallel hydraulic system may be used as an add-on on vehicles and does not necessarily address or solve the full energy consumption issues of those vehicles.
The conventional series hybrid hydraulic systems go beyond the parallel system, but lack a good and precise flow control speed. They have not solved, at low or acceptable cost, the recharge of the accumulator using the extra power of the prime mover when this is available.
Both the parallel and the series solutions and devices have a very significant handicap: steel accumulators can weigh more than fifty (50) times the weight of a lead-acid battery per unit of stored energy. When fiber made accumulators are used, the weight differential is still significant and can be about 12 to 1, but the price of making such as device increases greatly, making it in effect economically unfeasible. As a result, all or most, accumulators used for present hybrid hydraulic applications are generally quite small and may be usable only for short cycles, mainly for brake energy recuperation and release.
Both the parallel and series solutions, have major difficulties when the vehicle becomes larger in weight and/or dimension, almost all efforts have been devoted to automobiles, whereas the applicant solution is ideal for all applications, specially large vehicles either on wheels, tracks, tires or rail.
Furthermore, the scenario described above does not allow for those hydraulic systems to actually stop the engine, or the prime mover, when the accumulator is full and has energy available to propel the vehicle, as the vehicle will only run for a few seconds with the relatively small energy content of the accumulator. The presently available hydraulic systems, with few exceptions, are not configured or built to allow for this type of dual operating mode.
One aspect of this invention is therefore to address the limitations of the prior art systems by using a simpler and less expensive system, as well being able to not only significantly increase the efficiency of all terrestrial vehicles, but also to cut substantially their emissions.
In this specification, the term accumulator as the “frame” should be broadly interpreted to mean not only a single support frame for a vehicle but also could be a support frame having multiple tubular of equal or different dimensions and other components each tied together. Furthermore, in this specification the term “vehicle” also includes transportation, construction, industrial, mining and military moving devices, and other types of moving machinery.